On Sun, Feb 24, 2019 at 8:04 PM Rigel Hope <[email protected]> wrote:
> "For this use case it probably wouldn't even work since it can't do > network transfers." > > pipe to tar, pipe to netcat. sha256sum afterwards. > We needed to transition some VMs from one machine to another one, a year or so ago. The two machines were in the same data center but in different racks at different ISPs. When we cut over the VMs I wanted to minimize downtime. The VM storage allocations were something like 200GB each. Also, I discovered that rsync didn't know how to work on block devices. I think there was a patch floating around that let it work on block devices, but for whatever reason it wasn't practical. So, I dd'd the mounted block device, knowing full well that it wasn't stable, to a file on host A, and rsync'd that file across to host B. This took hours. Most of the block device would still be the same when I was ready to cut over. When we were ready to roll (in the middle of the night, hopefully), I shutdown the VM on host A, dd'd the block device to the file again, rsync'd the file across the network to a file on host B, dd'd that file to host B's block device and booted the VM back up on host B. The total downtime per VM was about 20 minutes, iirc. I'm sure I'm leaving out some details, as it was a while ago. I'm recalling copying and hand editing some kvm/qemu metadata as well. I'm not knocking "backup software", but I felt happier knowing that if something went wrong somewhere in the process, I'd know how to fix it. The main idea I try to follow is to leave a path of retreat and "bring the 60m rope". https://www.coldmountainkit.com/knowledge/historical-facts/toni-kurz-died-on-the-eiger/ -- Russell Senior [email protected] _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
